Tram-trains, which are being trialled in Yorkshire and are widely used in Europe, can run on both tram and train tracks.

They could be introduced in Edinburgh under plans by Network Rail to electrify the “South Sub” to divert more freight trains from running through Waverley. The tram-trains could run into the city centre before switching to tracks on streets.

Mr Verster was previously involved with the Yorkshire experiment in his last job as Network Rail’s London North East route managing director.

Mr Verster told the Holyrood’s infrastructure and capital investment committee yesterday that tram-trains “must be on the cards for so many cities”. He added: “They are a real practical solution to get footfall off the rail network.”

The South Sub, which arcs round the south side from near Murrayfield Stadium to Brunstane, lost its regular passenger trains more than 50 years ago, but is still used for diverted services and freight trains.

The Capital Rail Action Group, which has pressed for greater use of the line, said Mr Verster’s support was significant because the ScotRail Alliance covered both the train operator and track owner Network Rail.

Chair Lawrence Marshall said: “Tram-trains would ease the pressure on the existing railway and open up new travel opportunities for the city.”

He said a tram line could be built to link the South Sub to Edinburgh Royal Infirmary, just south of the line.

Committee convener and Edinburgh Southern SNP MSP Jim Eadie led a debate at Holyrood last month, which secured cross-party support for developing the line.

Transport minister Derek Mackay told MSPs in the Chamber: “I am happy to take the issue further, but I give a strong message that I want to see clear evidence from the [public-private co-ordinating body] South East of Scotland Transport Partnership and City of Edinburgh Council that the issue is a priority for them.”